In mobile radio communication systems or mobile radio communication networks, mobile terminals need to periodically perform different types of area update registrations. The mobile terminals perform these area update registrations for several reasons, such as, for example, to ensure that information about where a terminal is currently located is updated in the mobile radio communication system.
Also, for mobile terminals using IMS, where IMS is an acronym for IP Multimedia Subsystem, an IMS client residing in the mobile terminal may need to perform signalling towards an IMS core network, which normally include periodic registrations and presence signalling. These periodic registrations may be performed for similar reasons as for the periodic area update registrations or in order to be able to provide various IP-based services.
For a mobile terminal running an IMS client, it may follow that the mobile terminal has to perform these regular periodic registrations as each of the corresponding timers for these different periodic update registrations expire. This is a problem, since for each of these events a mobile terminal has to activate a transmitter. To repetitively activate and deactivate the transmitter as the different timers expire will inevitably lead to a short battery life time. This in turn will also lead to a reduced capacity and a short stand-by time for the mobile terminal. It may also cause the mobile terminals to use the system in a non optimal way by, for example, occupying additional system resources.
Additionally, since mobile terminals increasingly are fitted with more and more additional equipment, such as, for example, larger displays and more advanced applications, the need for and importance of saving battery life time has also increased.